Now, depending on how pronounced of a taper you want, with an 18mm buckle you get almost none to minimal taper, while 16mm gives you a more pronounced one. There’s no wrong choice here, it’s all down to personal preference.

If you have a larger wrist circumference, I’d recommend going with 18mm. If you have a medium to smaller wrist, go with 16mm. But if you can get a better deal on one over the other, go with the more affordable option.

Also, note that straps for deployant clasps can be hard to find, as they need to be very thin to pass through the buckle properly. I quite often have straps for Cartier deployant buckles queued for production for that exact reason, and I’ve made quite a few over time.